<title>malloc function</title>

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<h1>malloc function </h1>
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<b>malloc</b> (memory allocation) is used to dynamically allocate memory 
at run time. Possible uses for this function are:

<ul>
<li>Read records of an unknown length.
<li>Read an unknown number of database records.
<li><a href="../MISC/linklists.html">Link lists</a>.
</ul>

The simplest way to reserve memory is to code something like:
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<pre>

	main()
        {
            char string[1000];

            <a href="strcpy.html">strcpy</a> (string, "Some text");
        }
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The example above has two problems:
<ul>
<li>If the data is less than

1000 bytes we are wasting memory.
<li>If the data is greater than 1000 bytes the program is going to crash.
<li>The 1000 bytes are reserved throught out the life of the program.    
If this was a long running program that rarely used the memory, it would 
again be wasteful.
</ul>
malloc allows us to allocate exactly the correct amount of memory and 
with the use of <a href="free.html">free</a> only for the time it is required.
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<pre>
	Library:   stdlib.h

	Prototype: void *malloc(size_t size);

	Syntax:    char * String;

                   String = (char *) malloc(1000);
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Looking at the example syntax above, 1000 bytes are reserved and the pointer
<b>String</b> points to the first byte. The 1000 bytes are NOT initialized
by malloc. If the memory is NOT available, a 
<a href="../SYNTAX/null.html">NULL</a> pointer is returned.

Please note, the cast <a href="../CONCEPT/cast.html">cast</a> is required to 
return a pointer of the correct type.
<h2>Examples:</h2>

<img src="../../GRAPHICS/computer.gif"><a href="../EXAMPLES/linklst1.c"> example</a> 
program.

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<h2>See Also:</h2>
<img src=../../GRAPHICS/whiteball.gif>
<a href="../CONCEPT/data_types.html#char">char</a> data type.<p>
<img src=../../GRAPHICS/whiteball.gif>
<a href="free.html">free</a> function.<p>

<img src=../../GRAPHICS/whiteball.gif>
<a href="../SYNTAX/sizeof.html">sizeof</a> operator.<p>
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<font color=brown>
<h2>C++</h2>
<img src=../../GRAPHICS/whiteball.gif>
<a href="../../CPLUSPLUS/SYNTAX/new.html">new</a> is the C++ equivalent to malloc.<p>

<img src=../../GRAPHICS/whiteball.gif>
<a href="../../CPLUSPLUS/SYNTAX/delete.html">delete</a> is the C++ equivalent to 
<a href="free.html">free</a>.<p>
</font>

<p>

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<address><a href="../../address.html">Martin Leslie</a> 
</address><p>
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